(1) Field of the Invention
The present invention is directed to the extrusion of plastics, and more specifically to a method for achieving a very smooth extrudate surface using thermoplastic syntactic foam materials.
(2) Description of the Prior Art
Currently, technology is being sought that produces a very low-density, extrudable thermoplastic foam material with application to communication cable jacket materials for use in underwater applications. A new lower density foamed jacket with a smoother surface is required in order to improve the speed and underwater depth performance of several communication systems. The smoother the surface, the less drag will be exhibited while towing a cable underwater. A smoother surface will also result in improved jacket sealing and handling. Metallocene catalyzed polyolefin incorporating a thermoplastic syntactic foam material is ideally suited for producing a low density foam. Unfortunately this material exhibits a high degree of melt fracture during the extrusion process. As such, a smooth extrudate surface is difficult to achieve. What is needed, therefore, is a method of extruding metallocene catalyzed polyolefin incorporating a thermoplastic syntactic foam material in such a way as to produce a smooth extrudate surface that does not exhibit significant melt fracture during the extrusion process.